SSRL Imaging Group

With the high brightness of SPEAR3, imaging techniques over a wide range of length scales are being developed and added to the capabilities being made available to users, for various research projects in fields including biological, environmental, and materials science. Focused beams using mirrors, capillaries, and apertures are used to create x-ray beam sizes over a wide range, from a few microns to a few hundred microns. These techniques are used at beam lines 2-3, 10-2 and 14-3 to look at where different elements are located in a wide variety of samples, from soils, plants, tissue samples to ancient Greek artifacts. The focused beams not only can determine what elements are present in the sample, but also what the chemistry is of the element is at specific locations. A microscope employing zone plates to focus the beam is under development and will soon provide 30 nm beams to study properties of magnetic domains at Beam Line 13-1. Not only can x-rays be focused to probe materials in a small spot, but they are being used in an actual x-ray microscope, at Beam Line 6-2, that provides 2- and 3-dimensional images in real space at 30 nm resolution, showing objects ranging from biomaterials such as bones and teeth to advanced fuel cell materials and nanostructures. Rounding out SSRL's imaging capabilities is the lensless imaging station at Beam Line 13-3, which uses the two-dimensional pattern of soft x-rays scattered from the sample to image nanostructures at resolutions better than 30 nm. The extreme capabilities of the Linac Coherent Light Source will make it possible to use this technique to image objects at Ångström resolution.

These activities include efforts supported by DOE BES, NIH NIBIB, and the SSRL SMB Program supported by NIH NCRR and DOE BER.

Beam Line 2-3

The hard x-ray imaging station at BL 2-3 is a dedicated imaging facility which has the ability to perform a wide series of experiments, including x-ray fluorescence imaging, micro-spectroscopy (i.e. micro-XANES and micro-EXAFS), spectroscopic imaging (mapping an elemental distribution at several energies within the absorption edge of an element), micro-diffraction, and micro-tomography. The focused x-ray beam is acquired using Kirkpatrick-Baez (K-B) mirrors directly imaging the bending magnet source, and results in a beam size of approximately 2 x 2 microns and photon fluxes in the mid 108 photons/second in the focused spot with SPEAR current at 200mA. The energy range of the beam line optics at BL 2-3 covers from 5-23 keV, with detection of fluorescent x-rays as low as Si. Sample sizes are limited due to the travel range of the high-resolution sample positioner, which is 24 mm in the vertical and horizontal. For details please contact Sam Webb

Beam Line 6-2c

This full-field hard x-ray microscope is capable of imaging from 4-14 keV, with resolution up to 30 nm using micro zone plates. The field of view is 30 microns, but raster scanning can extend this to examine a wider range with full resolution. The incoming beam is focused using a capillary condenser, forming hollow cone illumination. It is capable of Zernike phase contrast at both 5.4 keV and 8 keV, enabling imaging of lower-absorption biological materials, and of 3D tomography. It also has a fluorescence detector for confirming elemental composition within a subset (~3 micron diameter) of the field of view. The TXM has been used to study mouse bone trabeculae, yeast cells, metal uptake in plants, and materials. For details please contact Joy Andrews Hayter or Piero Pianetta

Beam Line 10-2

The imaging station at BL 10-2 is used to perform rapid imaging on larger samples with larger beam sizes. The sample positioning stage has a total travel limit of 600 mm horizontally and 300 mm vertically. The beam size can be determined by pinhole apertures (50 to 250 microns) or glass capillary (~10 microns). Future upgrades may allow for the installation of a K-B mirror pair to attain beam sizes of ~2-5 microns. BL 10-2 uses a wiggler for the x-ray source and has x-ray fluxes approximately 10-50 times greater than BL 2-3. This provides a complementary set of abilities to be able to scan large areas (also good for survey scans of samples to be measured at higher resolution later at BL 2-3) or detect lower elemental concentrations. BL 10-2 is also capable of performing micro-spectroscopy and spectroscopic imaging. For details please contact Sam Webb or Apurva Mehta

Beam Line 13-1

In a scanning transmission x-ray microscope (STXM), spatial resolution is obtained by using zone plate lenses which focus the x-ray beam down to a spot size of 10s of nm. The sample is then scanned perpendicular to the optical axis, while the intensity of the transmitted x-rays is detected at the same time. Such a microscope is currently commissioned at SSRL BL13-1. It will initially provide a spatial resolution of about 35nm, while operating under UHV condition, at temperatures between 25K and 450K, as well as in applied magnetic fields. Because the microscope enables us to study systems in magnetic fields as well as in a wide temperature range, we anticipate that groups interested in research on magnetism and correlated materials will be particularly interested in this type of microscopy. For details please contact Hendrik Ohldag

Beam Line 13-3

The soft x-ray (150 - 1200 eV) coherent scattering beamline is capable of X-ray Fourier Transform Holography (FTH) and resonant Coherent Diffraction Imaging (CDI) with a flux of 2 x 107 photons s-1um-2 at the shortest transverse coherence of 3 um in a spot size of 25 x 250 um on the sample. The distance between the sample and the in-vacuum backside-illuminated CCD detector can be adjusted from 50 to 400 mm. The detector consists of 1340 x 1300 pixels of 20 um. Nanoscale imaging at cryogenic temperatures (15 - 300 K) and the application of magnetic fields up to 0.1 T are also available. Several novel lensless imaging techniques such as HERALDO and reference guided phase retrieval have been demonstrated at this beamline. With the use of a mobile laser hutch, optical pump x-ray probe experiments with picosecond time resolution are possible. In the future, the implementation of X-ray Photon Correlation Spectroscopy (XPCS) will enable observations of real-time dynamics in the microsecond - second range. For details please contact Hendrik Ohldag

Beam Line 14-3

Beam line 14-3 is a bending magnet side station dedicated to X-ray imaging and micro X-ray absorption spectroscopy of biological, biomedical, materials, and geological samples. BL 14-3 is equipped with specialized instrumentation for XRF imaging data collection in the intermediate X-ray regime of 2-5 KeV. A Kirkpatrick-Baez (KB) mirror system is used to achieve microfocus beam of 5 x 5 microns. BL 14-3 is ideal for obtaining elemental maps of small samples (~ 20 µm to 25 mm) as well as performing XANES on selected points in the sample. Experiments conducted on this beam line include XRF imaging, micro-XAS and XANES imaging. For details please contact Sam Webb